WASHINGTON (AFP) - Climate change is "largely irreversible" for the next 1,000 years even if carbon dioxide (CO2) emissions could be abruptly halted, according to a new study led by the US National Oceanic and Atmospheric Administration (NOAA).

The study's authors said there was "no going back" after the report showed that changes in surface temperature, rainfall and sea level are "largely irreversible for more than 1,000 years after CO2 emissions are completely stopped."

NOAA senior scientist Susan Solomon said the study, published in this week's Proceedings of the National Academy of Sciences journal, showed that current human choices on carbon dioxide emissions are set to "irreversibly change the planet."

Researchers examined the consequences of CO2 building up beyond present-day concentrations of 385 parts per million, and then completely stopping emissions after the peak. Before the industrial age CO2 in Earth's atmosphere amounted to only 280 parts per million.

The study found that CO2 levels are irreversibly impacting climate change, which will contribute to global sea level rise and rainfall changes in certain regions.

The authors emphasized that increases in CO2 that occur from 2000 to 2100 are set to "lock in" a sea level rise over the next 1,000 years.

Rising sea levels would cause "irreversible commitments to future changes in the geography of the Earth, since many coastal and island features would ultimately become submerged," the study said.

Decreases in rainfall that last for centuries can be expected to have a range of impacts, said the authors. Regional impacts include -- but are not limited to -- decreased human water supplies, increased fire frequency, ecosystem change and expanded deserts.

President Barack Obama today made the most contentious move of his young administration with an order, overturning a ban on federal funds to foreign family planning organisations that either offer abortions or provide information or counselling about abortion. The rule change continues the dismantling of George Bush's conservative policies. It is likely to encounter fierce criticism from the still robust anti-abortion movement.

It will allow US aid, usually through the US agency for international development, to flow to HIV/Aids clinics, birth-control providers and other organisations that advocate or provide counselling about abortion across the world. It is known as the "global gag rule" because it denies US taxpayer dollars to clinics that even mention abortion to women with unplanned pregnancies.

The rule was signed by President Ronald Reagan in 1984, overturned by Bill Clinton in 1993, and reinstated by Bush. Critics of the rule say it deprives the world's poor women of desperately needed medical care, while proponents say US tax dollars should not promote abortion.

Obama ends Global Gag rule.
LIZ SIDOTI and MATTHEW LE AP News

President Barack Obama on Friday quietly ended the Bush administration's ban on giving federal money to international groups that perform abortions or provide information on the option. Liberal groups welcomed the decision, while abortion rights foes criticized the president.

Known as the "Mexico City policy," the ban has been reinstated and then reversed by Republican and Democratic presidents since Ronald Reagan established it in 1984. Democrat Bill Clinton ended the ban in 1993, but Republican George W. Bush re-instituted it in 2001 as one of his first acts in office.

A White House spokesman, Bill Burton, said Obama signed an executive order on the ban, without coverage by the media, late Friday afternoon. That was in contrast to the midday signings with fanfare of executive orders on other subjects earlier in the week. Obama's action came one day after the 36th anniversary of the Supreme Court's landmark Roe v. Wade ruling that legalized abortion.

The Bush policy had banned U.S. taxpayer money, usually in the form of Agency for International Development funds, from going to international family planning groups that either offer abortions or provide information, counseling or referrals about abortion. The rule also had prohibited federal funding for groups that lobby to legalize abortion or promote it as a family planning method.